Organosilane mold lubricants

ABSTRACT

ALKOXYSILANES, SUCH AS (CH3)2SI(OC10H21)2 ARE LUBRICANTS FOR MOLDS UTILIZED IN THE CASTING OF METAL ARTICLES.

United States Patent Office 3,554,910 ORGANOSILANE MOLD LUBRICANTS Milton L. Johnson, Midland, Mich., assignor to Dow Corning Corporation, Midland, Mich., a corporation of Michigan No Drawing. Filed Oct. 17, 1968, Ser. No. 768,507

Int. Cl. Cm 1/50, 1/52 US. Cl. 25249.5 7 Claims ABSTRACT OF THE DISCLOSURE Alkoxysilanes, such as (CH Si(OC H are lubricants for molds utilized in the casting of metal articles.

This invention relates to alkoxysilanes as mold lubricants. In one aspect the invention relates to an improvement in the casting of molten metal.

Silicones are known as lubricants and release agents generally. Many organosilicon compounds cannot be used as mold lubricants for molding or casting metal articles because they form a material buildup on the surface of the mold. This material buildup is detrimental because of the close tolerances of certain cast metal part specifications. The buildup also results in the lack of a smooth clean surface on the cast part.

Other known silicone release agents and lubricants are not used in many die casting operations because the cast metal article cannot be painted, plated or chemically treated, during the finishing operation. This difiiculty is due to the fact that the metal surfaces contain traces of siloxane which are incompatible with organic constituents in the paint, plating bath compositions and of the like.

By the practice of the invention, wherein die casting molds are lubricated with certain alkoxysilanes, mold buildup is minimized and the molded articles do not contain any undesirable siloxanes on their surfaces. In addition, the alkoxysilanes can be easily emulsified to form a stable, readily dispersible lubricating composition.

It is an object of the invention to provide an improved mold lubricant.

Another object of the invention is to minimize mold buildup in die casting operations.

These and other objects of the invention will be apparent to one skilled in the art upon consideration of the following disclosure and appended claims.

According to the invention there is provided a method of lubricating molds utilized in the casting of metals comprising applying to the molding surfaces of the mold an organosilane of the general formula R Si(OR') in which R is a lower alkyl radical of not more than 6 carbon atoms, R is a higher alkyl radical containing from 8 to 30 carbon atoms, and a has a value of from 1 to 3.

In the above described alkoxysilanes, R can be any lower alkyl radical, such as the methyl, ethyl, isopropyl, butyl or hexyl groups. R is a higher alkyl radical, such as the octyl, decyl, dodecyl, tridecyl, octadecyl, C H C H and myricyl groups. R includes the normal and branched chain radicals. It is often convenient to use mixtures of the above silanes, thus R can be the same or different when a is 1 or 2.

The preferred R substituent is the methyl group. Because of their lower melting point and increased stability when emulsified silanes in which R is an alkyl of 10 to 14 carbon atoms are preferred,

The organosilanes utilized in the practice of the invention are the reaction products of R SiCl with a higher alcohol (R'OH), where R, R and a are as defined above. The silanes are readily made by known methods.

3,554,910 Patented Jan. 12, 1971 In one embodiment of the invention, the alkoxysilanes are applied to the mold surfaces in the form of an aqueous emulsion. Generally, the emulsion contains from 5 to weight percent of the organosilane and from 1 to 10 weight percent of an emulsifying agent, the rest being water. The emulsions can also contain minor amounts (0.1 to 2 weight percent) of stabilizers, such as freeze-thaw agents, and other additives, such as rust inhibitors.

While cationic emulsifying agents, such as aliphatic fatty amines, are operable in forming the emulsions utilized in the practice of the invention, nonionic and anionic emulsifying agents are preferred. Suitable nonionic emulsifying agents are the saponines; condensation products of fatty acids with ethylene oxide such as dodecyl ether of tetraethylene oxide; condensation products of ethylene oxide and sorbitan monolaurate; condensation products of ethylene oxide and sorbitan trioleate and condensation products of phenolic compounds having side chains with ethylene oxide such as condensation products of ethylene oxide with isododecylphenol or nonylphenol; and imine derivatives such as polymerized ethylene imine and N-octadecyl-N,N'-ethylene imide.

Suitable anionic emulsifying agents are a kali metal sulforicinates; sulfonated glyceryl esters of fatty acids such as sulfonated monogylcerides of coconut oil acids; salts of sulfonated monovalent alcohol esters such as sodium oleylisothyionate; amides of amino sulfonic acids such as the sodium salt of oleyl methyl tauride; sulfonated products of fatty acid nitriles such as palmitonitrile sulfonate; sulfonated aromatic hydrocarbons such as sodium a-naphthalene monosulfonate; condensation products of naphthalene sulfonic acids with formaldehyde; sodium octahydroanthracene sulfonate and alkylarylsulfonataes having one or several alkyl groups of 8 or less carbon atoms.

The organosilanes can also be dissolved in a suitable solvent such as aliphatic hydrocarbons, for example hexane; aromatic hydrocarbons, for example xylene and toluene; or chlorinated hydrocarbons, for example perchloroethylene; and then :be applied to the molding surfaces as a solution.

The organosilanes can be applied to the molding surfaces by conventional techniques, such as brushing, dipping, flooding of the mold, or spraying the material onto the mold. A preferred method utilizes the above-defined emulsions which have been further diluted with from 10 to 300 volumes of water and then sprayed into the interior of the mold prior to each casting cycle.

Both ferrous and non-ferrous metals can be casted into the mlods lubricated in accordance with the invention. Alloys of aluminum, zinc, lead, copper, tin and magnesium can be easily cast in the lubricated molds. Gravity casting methods, where the molten metal is poured into a mold, and pressure die casting methods, where the molten metal is forced into the mold, both benefit from the use of the alkoxysilane lubricant. It is conventional to lubricate these molds immediately prior to the casting operation. One measure of the efficiency of the lubricant is the number of molding cycles which can be made using a single mold before the material buildup in that mold necessitates cleaning. By the practice of the invention casting operations can be carried out with little or no down time for mold cleaning. Metal castings made with the lubricated molds do not present problems during painting or plating The following examples are illustrative of the invention which is defined in the claims.

3 EXAMPLE 1 An emulsion containing 35 weight percent 4 weight percent oleic acid, 2.3 weight percent morpholine, and 58.7 weight percent water was dispersed in water to form a lubricant of approximately 50 parts Water to 1 part emulsion. This lubricant was applied to an intricate mold to form aluminum castings by the pressure die casting method. The lubricant was sprayed into the mold prior to each molding cycle. After 1,000 molding cycles, there was no material buildup in the molds.

EXAMPLE 2 EXAMPLE 3 For purposes of comparison the same type of mold was lubricated with a dispersion of 1 part of a commercially available organosilicone emulsion in 50 parts water. After 100 molding cycles in the aluminum die casting operation, the mold showed a considerable buildup and if critical, it would have been necessary to halt the casting operation to clean the mold.

EXAMPLE 4 The emulsion described in Example 2 was diluted with 130 parts of water and utilized to lubricate aluminum valve body molds in a die casting operation. The material proved to be an excellent lubricant.

EXAMPLE 5 When the emulsion described in Example 2 was used at an 80 to 1 ratio with water as a lubricant for casting magnesium metal parts, test results were comparable to those obtained in Example 2.

Reasonable modification and variation are with the scope of the invention, which defines a novel method of lubricating the molds used in metal casting operations. An improved metal casting process results from the practice of the invention.

That which is claimed is:

l. A method of lubricating molds utilized in the casting of metal comprising applying to the molding surfaces of said mold an organosilane of the general formula in which R is a lower alkyl radical of not more than 6 carbon atoms;

R is a higher alkyl radical of from 8 to 30 carbon atoms; and

a has a value of from 1 to 3.

2. The method of claim 1 wherein said organosilane is applied in the form of an aqueous emulsion.

3. The method of claim 2 wherein said emulsion consists essentially of 5-60 weight percent of said organosilane; and 1-10 weight percent of an emulsifying agent; the balance being water.

4. The method of claim 3 wherein said emulsion is diluted with from 10 to 300 volumes of water per volume of emulsion prior to applying said emulsion.

5. The method of claim 1 wherein said organosilane is a mixture Of (CH3)2Si(OC12H25)2 and 6. The method of claim 1 wherein said organosilane is s)2 1s a7)2- 7. The method of claim 1 wherein R' is an alkyl radical of from 10 to 14 carbon atoms inclusive.

References Cited UNITED STATES PATENTS 2,129,281 9/1938 Lincoln et al. 25249.6 2,947,772 8/1960 Eynon et al. 25249.6X 2,985,678 5/1961 Chappelow et a1. 25249.6X 3,160,647 12/1964 Chappelow et al. 25249.6X

OTHER REFERENCES Aitchison et al.: The Casting of Non-Ferrous Ingots, Pub. by McDonald and Evans, Ltd. (1953).

DANIEL E. WYMAN, Primary Examiner W. E. CANNON, Assistant Examiner US. Cl. X.R. 

